Construction of ventilating fans



Dec. 17, 1940. c. M. lwusaBLnwfv 2,225,398.

CONSTRUCTION 0F VENTILTING FANS Filed Sept. 13, 1939 CM. HAN BUN INVENToR mlma, j

Patented Dec. 17, 1940 UNITED STATES PATENT oFFicE Application September 13, 1939, Serial No. 294.5991/2 7 Claims.

(Granted una" the se: or Mal-ch s, isss, as

amended April 30,.

This invention relates to improvements in the design of Ventilating fan housings or casings for the purpose of reducing the noise of the fan when operating. y

'I'he housing or casing of existing types of fans is constructed with single walls, usually of metal.

I'he object of this invention is to provide fan housings or casings with double walls and air space, preferably of cellular construction adapted l to reduce noise.

With the foregoing .and other objects in view. the invention consists in the construction, combination and arrangement of parts as will be described more fully hereafter.

In the drawing:

Fig. i is a vertical view of a centrifugal type Ventilating fan with part of housing broken away.

Fig. 2 is a vertical sectional view of Fig. 2 taken at 2-2. Fig. 3 is `a vertical sectional view of an axial flow type Ventilating fan.

Fig. 4 is a sectional view of Fig. 3 taken at 4-4. Fig. 5 is a sectional view of a portion of an alternate type of centrifugal fan housing construction.

Fig. 6 is a sectional view of an altematetype of wall construction to that shown in Fig. 1.

Fig. 7 is a sectional view of 1-1;

80 Fig. 8 is a sectional view of a second alternate type of wall construction to that shownin Fig. 1; and

Fig. 9 is a sectional view of another alternate type of wall construction.

85 Referring more in detail to the several views of the drawing and more particularly to Figs. 1 and 2:

There is shown at Il a Ventilating fan housing enclosing a centrifugal type fan wheel II driven by a motor I2 mounted on a base'll. 'I'he fan housing I0 has an air inlet I4 on one side, an end plate Il on the other side, an air outlet Ii, and is .supported from the motor frame by brackets I1. "I'he centrifugal fan housing I l constructed in scroll form has an inner wall Il with slots I9, an outer wall 20 and supporting sides 2i. The air space 22 between the inner and outer walls may be continuous for the length of the scroll but the preferred arrangement is tn have cells or resonators 23 formed by divisional walls 24. The double walled fan housing with or without cell divisions may be of metal sheet or plate, assembled by welding, brazing, riveting or bolting or may be of cast metal such as aluminum alloy,

butvthe preferred form is a housing of molded Fig. 6 taken atA plastic material such as Bakelite or the like. If the housing is of cast or molded material aportion of .the housing such 'as' outer wall 20 in Figs.

1 and 2 or end plate 25 on housing 2III in Fig. 6 is made removable or the housing IIII is divided 5 as at 26 in Fig. 5 to facilitate casting or molding. Additional cells or resonators may be provided on the side walls of the fan housing, as shown in Fig. 8.

In Figs. 6, 7 and 8, the inner walls 2I8 and III 10 are shown with orifices 2I9 and IIS instead of slots I9. Figs. 3 and 4 show the double walled construction applied to the housing of an axial flow fan in which the housing consisting of cells or resonators 423 formed by outer wall 420, di- 15 visional walls 424 and inner wall 4Il with slots 4I! incloses a motor 4I2 supported by brackets 21 and driving an axial flow type fan wheel having blades 2l with hub 29. Where the housing is of molded plastic material reinforcement may be 20 provided for supporting ,the motor, such as angle iron ring 30. In the various applications of this invention orifices may be substituted for slots or slots may be substituted for orifices as bestr suit /conditions of design. The slots and orifices have 25 rounded edges at the inner surface of the inner wall to avoid generation of noise at this point, as indicated at n in the figures of the drawing.

The space 22between the inner and outer walls, if continuous, or the isolated cells 22, |22, 223, l0 22,3 and 424 may be filled with sound absorbing material but the preferred arrangement is to design the air cells with suitable-spacing and area of' orifice or slot openings and air volumes in the l cells to form resonators for absorbing those frequencies generated by the fan which contain the greatest amounts of energy. A number of cells or resonators designed for different frequencies' may be used in the construction of a fan housing to form an acoustic wave filter for the nant frequencies.

Another arrangement shown in Fig. 7 is to provide orifices 3| in the division walls 224 between cells or resonators 223 so that the relation of the resonator volume and the area and spacing of 5,

orifice openings 2 I l in the inner wall and the area of orifice openings II in divisional walls causes noise reduction due to interference of the sound waves. Still another` arrangement shown in Fig. 9 is to make the outer wall discontinuous so that the cells or resonators formed by sections of the outer wall, the inner wall and the divisional walls are separate from each other, or to omit the outer wall of the fan housing and attach separate resu predomi- 4,0

onators 32 to openings 5i! at selected locations on the scroll or housing.

The invention described herein may be manufactured and/or used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Having thus set forth and disclosed the nature of this invention, what is claimed is:

i. A double walled fan housing having an air space between said walls, divisional walls extendingbetween said walls and dividing said air space into cells. the inner of said double walls being provided with openings communicating with each of said cells whereby each of said cells becomes a resonator adapted to reduce noise generated by the fan. y

2. A double walled fan housing having a space between said walls, divisional walls extending between said walls and dividing said space into cells, the inner of said double walls being provided with openings communicating with each of said cells, and sound absorbing material located in said cells.

3. A double walled fan housing having an air space between said walls, divisional walls extending between said walls and dividing said air space into cells, the inner of said double walls being provided with openings communicating with each of said cells, the size of said cells and the areas and spacing of said openings being so selected that each of said cells is resonant to a selected one of the sound frequencies generated by said fan, thereby adapting it to reduce noise.

4. A double walled fan housing having an air space between said walls, divisional walls extending betweensaid walls and dividing said air space into a group of cells, the inner of said double walls being provided with openings communicating with each of said cells, the size of said cells and the areas and spacing of said openings being so selected that each of said cells is resonant to a selected one of the sound frequencies generated by saidfan. the resonance of said group of cells being so selected as to cover more than one of said frequencies. thereby causing said housing to constitute a sound filter for reducing noise generated by the fan.

5. A double walled fan housing having an air space between said walls, divisional walls extending between said walls and dividing said air space into cells, the inner of said double walls being provided with openings communicating with each of said cells. the size of said cells and the areas and spacing of said openings being so selected that each of said cells is resonant to a selected one 'of the sound frequencies generated by said fan, said divisional walls being provided with openings whereby adjacent ones of said cells will operate to reduce noise by mutual interference of the sound waves given off thereby.

6. A fan housing comprising a fan enclosing wall having openings formed therein, means forming in conjunction with said wall a plurality of cells located exteriorly thereof, each of said cells communicating with at least one of said openings, the characteristics of said cells and the openings communicating therewith being so selected as to cause each of said cells to be resonant to a selected one of the sound frequencies senerated by said fan, whereby the noise generated by the fan will be reduced.

'7. A fan housing comprising a fan enclosing wall having openings formed therein, a plurality of structures attached to the exterior of said wall. each of said structures forming in conJunction with said wall at least one cell, each of said cells communicating with at least one of said openings, the characteristics of said cells and the openings communicating therewith being so selected that each of said cells is resonant to a selected one of the sound frequencies generated by said fan, whereby the noise generated by the fan will be reduced.

CLYDE M. HAMBLIN. 

